1. Field of the Invention
The present invention relates to an apparatus and a method for handover between heterogeneous networks in a broadband wireless communication system. More particularly, the present invention relates to an apparatus and a method for seamless handover from a border cell of a broadband wireless communication system to a heterogeneous network.
2. Description of the Related Art
High speed Internet services allow a user to access the Internet at a high data rate (at 1 Mbps or so). The high speed Internet services originated with wired services for a stationary user. However, the high speed Internet services have been extended to be provided wirelessly at anytime and anywhere to a mobile user using a portable terminal. Currently, high speed Internet services are supported by broadband wireless communication systems based on Institute of Electronics and Electrical Engineers (IEEE) 802.16 or wireless communication systems based on Wideband Code Division Multiple Access (WCDMA)/High Speed Downlink Packet Access (HSDPA).
While broadband wireless communication systems are used to service dense urban areas, heterogeneous communication systems (WCDMA/HSDPA or EVolution Data Only (EV-DO)) are used to service any area. Accordingly, in the broadband wireless communication system, a region between dense urban areas would not be serviced unless a base station is installed in that region. By contrast, in the heterogeneous communication system, a terminal would be serviced in every area. Hence, when the terminal travels outside the coverage of the broadband wireless communication system in the region between the dense urban areas, a call drop occurs. After the call drop, the terminal is no longer serviced unless it re-enters the broadband wireless communication system. If the terminal is a dual-mode dual-band terminal which can be serviced by both the heterogeneous communication system and the broadband wireless communication system, the terminal attempts to reconnect the call through the heterogeneous communication system after the call drop occurred in the broadband wireless communication system. However, when the dual-mode dual-band terminal travels outside the service coverage area of the broadband wireless communication system and suffers the call drop, there are no apparatus and method for handover between the broadband wireless communication system and the heterogeneous networks without service interruption.
With advances in mobile communications, 2.5th generation, 3rd generation and 4th generation networks coexist and ability to provide a dual-mode dual-band function requires accessibility to various communication networks. Therefore, when a dual-mode dual-band terminal gets out of a service coverage area of a broadband wireless communication system, what is needed is an apparatus and a method for seamless handover to a heterogeneous communication system.